The instant invention concerns a process for the production of a fancy yarn on open-end spinning devices in which sliver-like basic fiber material is opened into individual fibers and is fed in an air stream to an open-end spinning element, as well as a device to carry out this process.
In a known device of this type (DE-OS No. 2.953.527) corresponding to PCT Published Application No. 79/00489 the fancy-effect fiber material is opened by means of drawing rollers and the pieces of fancy-effect material thus produced are thrown by an air stream against a screen for the purpose of being conveyed on to the gap between a pair of rotating friction rollers, where they combine with the basic material and are twisted together into a yarn. By means of a programming mechanism which influences the drive of the drawing rollers for the production of the fancy-effect material pieces, the frequency length and the thickness of the fancy material pieces in the fancy yarn are determined. Such a drive, controlled by the programming mechanism, is expensive. Furthermore, only those effects can be produced which have been input into the program mechanism. Since such a program only has a limited range of variation it is unavoidable that variations repeat themselves, even where costly programming is involved. It is however desirable that if at all possible no repetitions of the variations occur in fancy yarn, or that variations repeat themselves only after long periods.
It is the objective of the instant invention to create a process and a device for the production of fancy yarns which makes it possible to obtain by a simple method maximum random distribution of the effects.
This objective is attained according to the invention in that the fancy-effect fiber material is conveyed at constant speed in form of a closed, i.e. uninterrupted fiber sliver to an air stream and in that fiber tufts are separated by this air stream, the fiber tufts thus separated being conveyed to the open-end spinning element together with the opened basic fiber material. The opening of the fiber material which produces the fancy effects is therefore not effected by a mechanically operating opening device, as was done previously, but by the suction effect of the flowing air to which this material is conveyed. The air flow separates the fibers in an uneven fashion from the forward end of the fiber sliver which is retained by a feeding device. The distribution of the fancy-effect fiber material within the finished fancy yarn is therefore random with respect to size and sequence of the fiber groups or fibers separated from the fiber sliver. To carry out the process, a normal conveying device without any controls suffices, since it is not necessary to control the effects by means of variable feeding of the fancy-effect fiber material. This inventive process is especially well suited for the production of yarns with color effects. The inventive process is also eminently suitable for thin yarns in which the effects cannot be produced in the desired fine gradations because of the slowness of the known device.
To obtain good opening of the fancy-effect fiber material and to avoid thread breakage which may be caused by oversized fiber tufts, the invention provides for a flowing speed of the air stream which is considerably greater thant that of the fancy-effect fiber material.
To assist the pneumatic opening of the fancy-effect fiber material, the latter is subjected to retention in further variants of the inventive process, immediately before being brought into the air stream.
In order to ensure good mixing of the individual fibers of the basic fiber material with the fancy-effect fiber material as well as uniform yarn output, a preferred variant of the inventive process provides for the fancy-effect material air stream and for the fiber tufts thus separated by this fancy-effect material air stream to be conveyed to the conveying air stream of the basic fiber material.
To give the individual fibers separated from the fancy-effect fiber material sufficient time for straightening, the fancy-effect fiber material is preferably conveyed to the air stream during the latter's acceleration.
The flow of the individual fibers separated from the basic fiber material is not affected when suitable provisions are made for the opening of the fancy-effect fiber material to occur before the end of air stream acceleration.
To avoid affecting the parallel orientation of the fibers as they are being conveyed, a suitable variant of the inventive process furthermore provides for the conveying air stream and for the fancy material air stream to flow essentially in the same direction before being combined.
The opening of the fiber material which produces the fancy effects is entirely pneumatic and not mechanical. Thus the intensity of the air stream acting upon the fiber material is of particular importance for the opening of the fiber sliver made up of the fancy-effect fiber material. To avoid raising the negative pressure prevailing at the open-end spinning element merely for the opening of the fiber tuft, the fancy-effect fiber material is preferably fed into the conveying air stream for the basic fiber material at the point of highest air speed.
Variation of the effects can be achieved with the same fiber slivers being fed if the constant feeding speed of the fancy-effect fiber material is adjusted according to the effects one wishes to obtain.
To produce effects with more than only two colors, the fancy-effect fiber material can also be fed in the form of several fiber slivers, whereby these two or more fancy-effect fiber slivers can also be fed at different constant speeds.
To carry out the process described, the fiber feeding channel is equipped with a feeding opening in accordance with the invention, through which the fancy-effect fiber material, delivered at constant speed by the feeding device, is fed to the fiber feeding channel. The opening of the fancy-effect fiber material into fiber tufts is thus effected purely by pneumatic means.
Since it has been shown that the pneumatic opening of the fancy-effect fiber material can be assisted considerably by guiding it over a tear-off edge, such a tear-off or retention edge is preferably provided between the feeding device and the first fiber feeding channel.
To provide the best conditions possible for the separation of fibers and fiber tufts in the air stream, the fiber channel can be fashioned with a profile having surfaces at which the air stream it carries flows at different speeds, whrerby the feeding opening is located in the zone of higher air flow speed within the fiber feeding channel. For this purpose a sliver guide is preferably provided to hold the fiber sliver in the zone of greater air flow speed.
To ensure that the individual fibers separated from the basic fiber material as well as from the fancy-effect fiber material can stabilize before reaching the open-end spinning element, the invention provides for a fiber feeding channel with a tapering segment followed by a cylindrical segment, the feeding opening being located in the tapering segment of said fiber feeding channel.
According to the invention, opening of the fiber sliver made up of fancy-effect fiber material is to occur sufficiently early in the air stream so that the fiber sliver does not affect the orientation of the individual fibers separated from the basic fiber material. This is achieved according to this invention by means of the feeding opening consisting of the end of a fiber feeding channel for the fancy-effect fiber material, the length of which channel exceeds the maximum staple length of the individual fibers contained in the fancy-effect fiber material.
In order for the negative spinning air pressure to be as effective as possible within the second fiber feeding channel, thus ensuring thorough opening of the fancy-effect fiber material which is exposed to the air stream in form of a fiber sliver, the invention provides, in a preferred embodiment, that the fiber feeding channel for the fancy-effect fiber material lets out into the fiber feeding channel for the basic fiber material essentially in the longitudinal sense of the latter. If the fiber feeding channel for the basic fiber material starts out tangentially from an opening roller, the fiber feeding channel for the fancy-effect fiber material in a preferred embodiment of the object of the invention constitutes a rear extension of the fiber feeding channel for the basic fiber material.
To avoid excessive opening of the fancy-effect fiber material so that it may remain in the form of tufts even after pneumatic separation from the fiber sliver, the invention provides for the fancy-effect fiber material to be fed into the basic fiber material as it travels between the opening roller for the basic fiber material and the open-end spinning element. In order to attain nevertheless early feeding and thereby good mixing of the fibers, provisions can be made in a further embodiment of the object of the invention for a widening of the interior of the opening roller housing in the area where the fiber feeding channel for the basic fiber material begins, whereby the fiber feeding channel for the fancy-effect fiber material lets out tangentially to the opening roller into said widening.
It has been shown that without changing the device generally described above, normal yarn without fancy effect can also be spun by not feeding any fancy-effect fiber material to the feeding opening therefor. The air sucked in through the feeding opening does not affect the normal spinning process. However, it is also possible to provide a closing element for such feeding opening in a further embodiment of the invention, if this should be deemed to be conducive to better control of air flow conditions. Preferably this closing element is located in the area of the unopened fiber sliver so that no fibers already separated from the fiber sliver may catch on it when a fancy-effect yarn is being produced.
The feeding device is preferably equipped with an adjustable deive so that the constant feeding speed of the fancy-effect fiber material can be varied in relation to the basic fiber material.
According to the invention the feeding device for the fancy-effect fiber material can include a pair of rollers, or drawing equipment, whereby the draft within the drawing equipment is set so that the fiber sliver drawn in the drawing equipment is not opened into individual fibers but still remains in the form of a fiber sliver when leaving the drawing equipment, so that the separation of fiber tufts may only be effected pneumatically by a stream of air.
To increase the variety of possible fancy effects, several feeding devices and feeding openings for the feeding of fancy-effect fiber material into the fiber feeding channel can be provided.
The instant invention makes it possible to produce a deformation-resistant fancy-effect yarn, in particular a yarn with color effects, simply and without sliver preparation and chance variation, whereby the effects with respect to sequence and size are left to chance. The opening of the fancy-effect fiber material is not effected by mechanical means, so that none of the conventional opening devices are required for the fancy-effect fiber material. If the presented fiber material is still too thick for direct, pneumatic opening, the pair of rollers of the feeding device can be fashioned with the outlet roller pair of conventional drawing equipment which however draws the presented fiber material only to the extent that a closed, i.e. uninterrupted fiber sliver emerges from this drawing equipment. This fiber sliver is then opened by pneumatic means only. In this way irregular opening of the sliver-shaped fancy-effect fiber material is achieved without any special, randomly controllable and driveable opening equipment being required. The configuration of the device according to invention is thus a very simple one. Also, it is not necessary in an advantageous embodiment of the device according to invention to increase the negative spinning air pressure which produces the air stream for the opening of the fiber sliver from the pressure used in the normal spinning process, so that a device in accordance with the invention is not only simple in construction but also economical in operation.